With the continuing high price of oil and its increasing importation costs in many countries, the production of alternative fuel products (“biofuels”) is becoming increasingly important. A significant amount of research in the field has focussed on the conversion of lignocellulosic matter into fuel products such as ethanol to provide an alternative and renewable feedstock to the depleting sources of hydrocarbon-based raw materials.
Lignocellulosic matter consists of carbohydrate polymers (celluloses and hemicelluloses) and the phenolic polymer lignin. Existing technologies for the conversion of lignocellulosic matter into fuel products generally utilize a series of steps involving fractionation of the biomass followed by saccharification and fermentation. The saccharification and fermentation steps are often complex and add significantly to the cost of the process. Further, the hydrolysis of cellulose and hemicellulose into simple sugars suitable for fermentation is significantly hindered by the presence of tightly bound lignin. Existing technologies expend significant energy in decreasing the lignin content of sugar-containing fractions in order to increase accessibility by hydrolytic enzymes.
Lignin makes up a significant proportion of lignocellulosic matter and offers another utilizable resource in addition to the cellulosic and hemicellulosic components. However, a large proportion of biomass conversion methods fail to effectively utilize the lignin component which instead goes to waste. Additionally, many of the existing processes yield only ethanol. While ethanol is usable as a fuel, the energy content on a volume basis is about 30% less than currently used fossil fuels, and is not practical in current diesel engines. Ethanol also attracts water, which makes storage and handling difficult.
A need exists for improved methods of converting lignocellulosic matter into energy-containing products such as biofuels. A need also exists for biofuel production methods that better exploit the energy-producing potential of lignin.